The present invention relates to the general field of making an elongate mechanical part out of composite material, such a part having a lug at at least one of its ends for receiving a pin to provide a pivot connection with another part, and being stressed in operation both in traction and in compression.
A nonlimiting example of an application of the invention lies in making side-braces for landing gear.
A landing gear side-brace serves to take up lateral forces exerted on the landing gear and to keep it deployed after making contact with the ground. Typically, a side-brace comprises two arms that are hinged to each other and to other parts of the landing gear via their ends, by pivot connections.
In operation, such a mechanical part is subjected to high levels of mechanical force, mainly in compression and in traction, which forces are oriented along the longitudinal axis of the part (i.e. the axis passing through both ends of the part). Such parts are generally made out of alloys of steel, aluminum, or titanium.
In order to reduce the weight of such mechanical parts, proposals have been made to make them out of composite material. However, making such parts out of composite material raises various problems. In particular, given the limitations of composite materials concerning their ability to withstand hammering, the lugs of such parts are generally over-dimensioned, giving rise to the metal parts constituting interfaces with other parts of the landing gear also being over-dimensioned. Furthermore, such parts made of composite material present poor impact strength and a high risk of delamination, i.e. of their fiber layers separating, as a result of the repeated forces to which the part is subjected. Finally, the costs of fabricating such parts are high.
In order to satisfy these requirements, document EP 1 736 674 proposes making such mechanical parts out of composite material from a central fiber preform and a peripheral fiber preform, which preforms are obtained by three-dimensional weaving, the peripheral preform surrounding the central preform in such a manner as to leave at least one empty space at each of the two ends of the part between the two preforms, which spaces are for use in hinging with other parts. Metal inserts are housed in those spaces. That mechanical part thus presents an improvement in terms of hammering for traction forces on the lug.